hair and the sweater—f/8 at 1/125 or so. If you take a picture using these
settings, the skirt will be rendered correctly as gray. Other areas will also be
rendered correctly; dark areas like the hair will be dark and the light areas like
the sweater will be light.
So three entirely different readings are possible for the exact same subject,
depending on which portion of the scene fills the viewfinder when you take a
meter reading. In this case, the most correct exposure comes when the meter
reads from the gray skirt. Note that most of the time, you don’t have a gray
subject to meter from; instead you are reading a blend of darks, grays, and
lights and hoping they will average out to a middle gray—much like the skirt.
Handheld Meters
Most photographers use an in-camera TTL meter, but some use a separate,
handheld meter and set the f-stop and shutter speed manually. A variety of
models are available, ranging from simple and inexpensive to sophisticated and
costly; some even cost more than a good basic 35mm SLR camera.
The most obvious reason to use a handheld meter is if your camera does not
have a built-in meter. Many sophisticated medium-format models, and virtually
all large-format models, are meterless. And some photographers use older
35mm cameras that don’t have TTL meters. Even if your older camera has a
meter, it may not be very accurate or in good working condition.
Because a handheld meter is independent of the camera, you can easily bring
it up close to the subject for precise readings. This is particularly convenient
when you use your camera on a tripod. If you use your camera’s TTL meter, you
may face situations in which you must take the camera off the tripod, bring it up
close to the subject to take the reading, then reattach the camera to the tripod.
Most handheld meters also offer an entirely different way of reading light
than TTL meters. All TTL meters measure reflected light—the light bouncing
off the subject. Handheld meters also measure reflected light, but most are able
to measure incident light, the light falling on the subject, as well.
Some photographers feel that a handheld meter can help provide more accurate
film exposure, or that they have better control and understanding of exposure
by working with a separate meter. This opinion is somewhat subjective,
however. You should get good results if you use either type of meter correctly.
All meters are designed to produce middle gray, but they may measure light in
very different ways. Modern cameras with TTL meters usually offer a variety
of metering patterns, the meter’s method of analyzing the light from a scene for
good film exposure.
Be very careful which metering pattern you use. It’s quite possible to get a
different exposure recommendation from one pattern than from another, even
with the same subject. Usually such differences are not extreme, but they may
be enough to make the difference between a well-exposed negative and one that’s
hard to print.
On some cameras you choose the metering pattern by setting a switch. On
others you turn a dial. And on most modern models you turn a control wheel
or press a button until you see the desired icon (or some other marking) displayed
on a screen or in the viewfinder. Many, but not all, cameras offer the
following metering patterns: centerweighted, multisegment, and spot.
Centerweighted metering. Some camera meters use centerweighted metering as
their default pattern. This means the meter averages all the light in the viewfinder,
but gives more consideration to the center when calculating exposure.
Centerweighted metering presumes that the main subject of the photograph is
in the middle of the frame—a reasonable assumption, as most photographs are
more or less composed that way.
Different camera models have varying methods of centerweighting. Some
might assign 60 percent of their exposure calculation to the center of the viewfinder,
while others might assign 80 percent, leaving the rest of the viewfinder
to contribute 20–40 percent to the exposure calculation.
Choose a centerweighted metering pattern for normal subjects. Such subjects
include those positioned more or less in the middle of the frame, where there are no unusually bright or dark areas and/or the overall tones average out more
or less to middle gray.
Multisegment metering. Multisegment metering, also called matrix or evaluative
metering, relies heavily on computer technology. The viewfinder is divided
into segments of varying shapes and sizes, and the meter analyzes each segment
individually to suggest a suitable f-stop and shutter speed for the overall exposure.
Multisegment meters can be quite sophisticated, even comparing the light
values of the current scene in the viewfinder against preprogrammed patterns
stored in memory.
Multisegment meters are particularly useful for scenes where light and dark
areas are not evenly distributed, such as when your subject is backlit or when
you have extreme light or dark areas in any part of your picture. For instance,
if your picture includes very bright sky in one corner, the multisegment meter
discounts this corner’s importance when recommending exposure settings.
Some multisegment meters divide the viewfinder into three or four segments,
while others divide it into dozens of segments or more. The segmented areas are
not equal; some are larger than others and some are shaped differently.
Some cameras link multisegment metering to their autofocus system, giving
more weight to the segments that are close to the focused area. The presumption
is that most of the time you are focused on the main subject, and that is the
subject needing the most attention. This feature helps provide accurate exposure
readings even when a subject is off-center in the viewfinder.
Such features make multisegmenting the most accurate metering option in
most cases, especially when you are photographing quickly and in automatic
exposure mode. However, it is not foolproof. For example, you may still have
to adjust your exposure at times, particularly when your main subject is strongly
backlit or when it is a relatively small part of the picture.
Spot metering. Spot metering, a useful metering option not available on all
cameras, concentrates its reading in a small circle located in the center of the
viewfinder. It will take a reading only in the area of the subject in the circle and
ignore the rest of the viewfinder when making its f-stop and shutter speed
recommendations. For example, if your subject is wearing a black sweater and
you point the camera so that the sweater fills the circle, the meter will read only
the sweater’s black tones, even if the rest of the picture is a balanced combination
of light and dark areas.
Thus you must be very careful where you point the spot meter or you may
get an inaccurate reading for the overall picture. If the circle doesn’t contain a
gray tone, you will have to adjust the meter reading to compensate.
Niciun comentariu:
Trimiteți un comentariu